Production of oscillations from piezo electric crystals



July 5, 1932. A. Mc| NICOLSON 1,866,267

PRODUCTION OF OSCILLATIONS FROM PIEZO ELECTRIC CRYSTALS Filed Jan. 24, 192'? o 'Io Wo'. o n o Patented July 5, 1932 UNITED STATES PATENT orricng ALEXANDER MCLEA NICOLSO'N, OF kNEW YORK, N. Y., ASSIGNOR, BY MESNK'E ASSIGN- MENTS, TO WIRED RADIO, INC., F NEW YORK, N. Y., A CORPORATION OF DELA'V 1 WARE PRODUCTION s OF OSCILLATIONS FROM PIEZO ELECTRIC CRYSTALS Application led January 24, 1927. Serial No. 163,273.

My invention relates broadly to a system for the production of electrical oscillations and more particularly to a circuit arrangement for the generation of oscillationsv derived from piezo electric crystal elements.

One of the objects of my invention' is to provide a system for generating oscillations by a piezo electric crystal controlled gen-erator system whereby oscillations of a frequency lower than the natural frequencies of the piezo electric elements may be derived.

Another object of my invention is to provide a system for the production of didei`- ential beats or a third frequency from a piezo electric crystal controlled generator system where the differential beats mayhave a frequency within the audible range.

Another. object of my invention is to prop'vide a ypiezo electric crystal controlled generator system by which oscillations within the audible frequency range may be derivedwithout the vemployment of cumbersome piezo electric crystal devices with all the inherent difficulties in the preparation of piezo electric crystals of large size.

,A further object of my invention is to provide a piezo electric crystal controlled generator system in which a plurality of piezo electric .crystal elements, each arranged to vibrate in a plurality of modes are connected with resonant circuits arranged to sustain oscillations at the natural frequency pos` sessed by the piezo electric crystal elements for combining the effects thereof for the productionl of a frequency within the audible range.

Another object ofimy invention is to pro-L vide a piezo electric generator system wheres in piezo electric crystal elements each adapted to vibrate in a plurality ofmodes yand at a plurality'of different frequencies are pro vided where the piezo electric crystal elements may be variably loaded for selectively adjusting the frequencies which are sustained by the associated electrical circuits.

'Still another object ofthe inventionis `to provide a circuit arrangement for simultaneously controlling the frequency of a plurality of oscillations `of different frequencies by means of piezo electric` frequency controlled devices, each arranged to vibrate in a plurality of modes. f

My invention will be more clearly understood from the specification hereinafter following by reference to the accompanying drawing, in which: Figure l, shows the circuit arrangement of the vpiezo electric crystal elements in association with an electron tube circuit arranged in accordance with the principle of my invention; Fig. 2, shows a mounting for the piezo electric crystal kelements as employed in the oscillator system of my invention and Figure 3, is a plan view of the piezo electric crystal apparatus employed in the generator circuits of my invention.

My invention contemplates the production of oscillations within the audible frequency range by means of piezo electric crystal ele` ments without the necessity of employing piezo electric crystal elements of cumbersome size. Under certain conditions it has been impractical to generate oscillations within the audible frequency range by reason of the large physical size of the piezo electric crystal element having a natural frequency corresponding to an audible frequency. By the circuit arrangement of my invention, l provide piezo electric crystal elements, each capable of vibration in a plurality of different modes and at a plurality of different frequencies, the piezo electric crystal elements being selected with respect to their natural frequencies for the deriva-l tion of differential beats or third frequency proportioned .to the principal frequencies. This beat or third frequency may be within the audible range or the third frequency may be above the audible` range dependent upon the natural frequencies of the piezo electric crystal elements. F or the purpose of explaining my invention, I have illustrated the same as employing piezoelectric crystal yelements possessing the property oftorsional vvibration At the same time that `the piezo lil tal elements are included are provided with a plurality of resonant circuits for sustaining oscillations of selected frequencies. An electron tube system is provided to which the several resonant circuits are connected and by which the' several generated frcquencies may be combined to produce by their sum or difference, frequency which may be ultimately delivered to a circuit common to the several circuits of the oscillator system. In order to niinutely adjust the relation of the several frequencies which are impressed upon the electron tube oscillator circuits -l provide means for mounting the piezo electric crystal elements in such manner that the piezo electric crystal elements may be subjected kto conditions of variable loading through a mechanically coupled system. By mechanically coupling the piezo electric crystal elements, which are electrically connected in different resonant circuits associated with tue input and output circuits of an electron tube system, there is provided an oscillatory system by which a differential beat frequency may be derived and slightly varied in a positive or negative direction by a variation in the loading producing a change in the natural period of vibration of the mechanical coupling between the piezo electric crystal elements. l he differential frequency thus produced. may be employed for a variety of purposes. The ease of control of such frequencies and the fixing of the frequency at a constant value render the system of my invention adaptable for many types of control circuits Where a constant frequency source is of extreme importance.

Referring to the drawing in more detail, reference character 1 designates an electron tube having a cathode or filament elect-rode 1a, grid electrode 1b and plate electrode 1c. Input circuit i2 connects across the grid and filament electrodes and an output circuit 3 connects across the plate and lilament electrodes.

The input circuit 2 includes an inductance system 4 `While the output circuit 3 includes inductance system 5 and the high potential source 6. rThe cathode of filament electrode 1a is heated from battery 7. The input and outputcircuits are interlinled by means of the frequency determining circuits which constitute an important part of my invention. l have illustrated sets of piezo electric crystal elements represented more clearly in Figs. 2 and 3 which are connected in resonant circuits which are in turn coupled to the in* put and output circuits of the oscillator. I have shown piezo electric crystal elements 19 and 2() mechanically coupled by means of an extremely light couplingmember 23. Tdach piezo electric crystal element is free to vibrate by reason of a special mounting such as of sponge rubber 28 and 29er glass Wool carried in standards 26 and 27. Piezo electric crystal element 19 is provided With electrodes 19a and 19?).

The piezo electric element is provided With electrodes 20a and 205 Which provide electric terminals for each of the piezo elec tric crystal elements. The linkage 2B provided With the laterally extending strut carries a movable mass represented by screw threaded nuts 24 and by changing the posi-- tion of this mass, a change in the `rate of vib 1ation of the piezo electric crystal system may be effected.

The piezo electric crystal system constituted by piezo electric crystal elements 10 and 11 is similarly arranged. That is, piezo electric crystal 10 has terminal electrodes 10a and 10b While piezo electric crystal element 11 has terminal electrodes 11a and 11b. The mechanical linkage or coupling 12 between the piezo electric crystal elements is provided With a laterally extended strut 18 on which the mass 1st is variably adjustable. The adjustment of the mass 14 or 24 on the struts 13 and 25 respectively causes changes in the natural frequency of the system.

Connected across the electrodes of each piezo electric crystal element, I providecircuits which may be made resonant to the natural frequency of the piezo electric crystal element in any selected mode thereof. Across the piezo electric crystal element 10, I provide a resonant circuit constituted by inductance 8 and variable capacity 9. The inductance 8 is variably coupled to inductance et in the input circuit 2. Piezo electric crystal element 19 has its opposite terminals connected across a resonant circuit constituted by inductance 17 and variable condenser 18. The inductance 17 is variably coupled to in ductance t in the input circuit 2.

The piezo electric crystal element 20 has its terminals connected across inductance 22 and variable condenser Q1 Where the inductance 2Q is variably coupled With the inductance 5 in the output circuit 3 of the electron tube 1.A 1n a similar manner7 piezo electric crystal element 11 has its terminals connected to a resonant circuit including inductance 15 and variable condenser 16, where the inductance 15 is vuriably coupled with the inductance 5 in the output circuit `3. By choosing the nature and dimensions of the piezo electric crystal elements and the mechanical coupling7 the natural frequencies thereof may be so combined through the coupling with the input and output circuits of the electron tube 1 as to derive oscillations of a frequency within the audible range, if desired, which are transferred to inductance 31 of an output circuit The several independent frequencies are inter-modulated in the electron tube circuits so that the resulting frequency may be the sum or difference of the frequencies originally impressed upon the electron tube circuits from the resonant IBO circuits. There may be oscillations at a 'pluralityof natural frequenciesimpressed upon the electron tube circuits for the development of the desired constant frequency which is suppliedto the output circuit. By adjustc ment of the periodicities of the several resonant circuits, the combined effects vof the natural oscillations in any desired Inode from the piezo electric crystal elements may be integrated in the electron tube circuits.

While I have illustrated one preferred embodiment of my invention, I desire that it be understoodv that modifications may be made and that no limitations upon my invention are intended other than are imposed by the scope of the appended claims.

What I claim as new .and desire to secure by Letters Patent of the United States is as follows:

1. An oscillation generator comprising means forgenerating a plurality of different frequency oscillations, a piezo electric device having a plurality of crystal elements traversed :by said oscillations and vibrating at a plurality of natural'frequencies corresponding to the frequency of each of said oscillations, and means mechanically linking the crystal elements of said device for crystalstressing to modify the frequency of the oscillations developed by said piezo electric device. j

2. In an oscillation generator, a space discharge device, a circuit so associated with said device that oscillations of a plurality of frequencies are generated therein, means f comprising a piezo electric device havinga plurality of crystals and a resonant circuit for simultaneously determining the frequencyy of all of said oscillations and means including a linkage member between said crystals for variably stressing said piezo electric device for fixing the frequency at which said device sustains oscillations.

3. In a space discharge tube system athreeelectrode space discharge tubeinput and output circuits for said tube, said circuits being coupled to produce continuous oscillations of a plurality of frequencies, a piezo electric device including a plurality of crystals for maintaining the frequency of said oscillations constant, and means including a weighted member interconnectin said crystals for mechanically and adjusta lyk lstressing said piezo electric device for changing the periodicity of said device. v v f v 4. In an oscillation generating system a space discharge tube,"a piezo electric device having a pair of crystals, a circuit including said tube and said device having generated therein a plurality of continuous waves of frequencies above audibility, means for obtaining from said vwaves a wave ofkaudible frequency, and means mechanically interconnecting said crystals for distorting said piezo electricy device under stress of vmechanical forces for adjusting the control of said audible frequencywave as to frequency by said piezo electric device.

c 5. An oscillation generator comprising a space discharge tube, means coupling the input and output circuits of said space dis'- charge tube, a piezo electric crystal device, said piezo electric crystal device being divided into two portions mechanically coupled one to the other, a resonant circuit con- 'l5 nected across each portion of said piezo electric crystal device said resonant circuits being coupled' to the input and output circuitsv of said space discharge tube, said piezo electric device `operating to determine the frequlency of the circuits of said space discharge tu e. v .c

6. In an oscillation generator system comprising an electron tube having input and output circuits, inductancesr interposed in each of said circuits and a plurality of piezo electriccry'stals adapted to be mechanically adj ustably distorted, a weighted member cooperating with said crystals to mechanically interconnect they same, each said crystal connected in separate resonant circuits, each of said resonant circuits coupled with the inductances in said circuits whereby a differential frequency is produced in said circuits.

7. An oscillation generator system comprising an electron tube having grid, lament and plate electrodes, input andoutput circuits interconnecting said electrodes, inductances interposed in each of said circuits,

a pair of piezo electric crystals adapted to 10o be mechanically andadjustably distorted, a link member mechanically coupling said crystals together, a resonant circuit connected across each of said piezo electric crystals,

the resonant circuits of each of said piezo electric crystals being electrically coupled with the inductances in said input and output circuits, respectively, for the production of oscillations of a differential frequency with respect to the oscillations of each of said-11o piezo electric crystal elements.

l 8. A wave generator system comprising a plurality of resonant circuits including piezoelectric elements for sustaining oscillations of-selected frequencies, an electron tube oscillator circuit systemV coupled to the several resonant circuits for combining the several generated frequencies, an audio frequency circuit responsive to saidelectron tube system, each of said piezo elements being adapted to vibrate in aplurality of modes and at a plurality of different frequencies and being .c selected with respect to their frequency characteristics for the derivation of differential beats proportioned to said frequencies, andV means mechanically interconnecting said piezo elements for variably mechanically distorting the same for selectively adjusting the relation of the several frequencies impressed n upon' said electron tube oscillator circuit. i, 130

f circuits coupled to said inductance systems, said frequency-deter?lining circuits including resonant circuits coupled to said input and output circuits and flexibly mounted sets of piezo-electric crystal elements connected in said resonant circuits, said setshaying a plurality of piezo elements mechanically coupled by an extremely light coupling member having an adjustable weight or mass tor adjusting the vibration periods of the piezo sets y by flexing or bending the individual piezo plates.

l0. An oscillator comprising a space-discharge tube, input and output circuits or said tube each including an inductance system, a. plurality or frequency-determining circuits coupled to said inductan'ce systems, said requency-determining circuits including resonant circuits coupled to said input and output circuits and liexibly mounted sets of piezo-electric crystal elements connected in said resonant circuits, said sets having a plurality ot piezo elements mechanically coupled by an extremely light coupling member haV- ing an adjustable Weight or mass for adjusting the internal stresses in said piezo elements and the consequent Vibration periods thereof.

11. resonator comprising an oscillation circuit, a requency-determining system for said oscillation circuit, said frequency-determining system including adjustable frequency piezo-electric apparatus comprising a plurality or crystals flexibly mounted and mechanically connected by non-piezo electric material, said material including an adjustable Weight for varying the tension and compression orces on said crystals and Simultaneously varying their frequency characteristics. f

l2. i resonator comprising an oscillation circuit, a frequency-determining System for said oscillation circuit, said Jfrequency-determining system having adjustable frequency piezo-electric apparatus including a device having piezo-electric properties and loading means Jfor bending said devicel to adjustably vary its frequency characteristics.

13. A resonator comprising an oscillation circuit, a frequency-c etermining system for said oscillation circuit, said frequencydetermining system having adjustable frequency piezo-electric apparatus including a plurality of crystals and loading means mechanically and adjustably interconnecting` said crystals Jfor bending the same to adjustably Vary their frequency characteristics.

14. il resonator comprising an oscillation circuit, a frequencydeterminingsystem for said oscillation circuit, said frequency-determining system having adjustable `frequency With respect to the Weight of its associated crystal.

In testimony whereof l aiiix my signature.

ALEXANDER McLEAN NIVCOLSON. 

